Potassium channels play an important role in regulating cell membrane excitability. When the potassium channels open, changes in the electrical potential across the cell membrane occur and result in a more polarized state. A number of diseases or conditions may be treated with therapeutic agents that open potassium channels; see (K. Lawson, Pharmacol. Ther., v. 70, pp. 39-63 (1996)); (D. R. Gehlert et al., Prog. Neuro-Psychopharmacol & Biol. Psychiat., v. 18, pp. 1093-1102 (1994)); (M. Gopalakrishnan et al., Drug Development Research, v. 28, pp. 95-127 (1993)); (J. E. Freedman et al., The Neuroscientist, v. 2, pp. 145-152 (1996)); (D. E. Nurse et al., Br. J. Urol., v. 68 pp. 27-31 (1991)); (B. B. Howe et al., J. Pharmacol. Exp. Ther., v. 274 pp. 884-890 (1995)); and (D. Spanswick et al., Nature, v. 390 pp. 521-25 (Dec. 4, 1997)). Such diseases or conditions include asthma, epilepsy, hypertension, male sexual dysfimction, female sexual dysfunction, migraine, pain, urinary incontinence, stroke, Raynaud's Syndrome, eating disorders, finctional bowel disorders, and neurodegeneration.
Potassium channel openers also act as smooth muscle relaxants. Because urinary incontinence can result from the spontaneous, uncontrolled contractions of the smooth muscle of the bladder, the ability of potassium channel openers to hyperpolarize bladder cells and relax bladder smooth muscle provides a method to ameliorate or prevent urinary incontinence.
U.S. Pat. No. 4,918,074, EP 183848 B1, EP 217142, EP 328700, JP 63060985, JP 63243029, JP 61227584, and Atwal, K.S., Bioorg. Med. Chem. Lett (1991) 1, 291-294 disclose bicyclic 4,7-dihydropyrazolo[1,5-a]pyrimidines.
The compounds of the present invention are novel, hyperpolarize cell membranes, open potassium channels, relax smooth muscle cells, inhibit bladder contractions, and are useful for treating diseases that can be ameliorated by opening potassium channels.